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DB2 - Problembeschreibung

Problem IC66162 Status: Geschlossen

Control dynamic downward adjustment of FCM resources

Produkt:
DB2 FOR LUW / DB2FORLUW / 950 - DB2
Problembeschreibung:
Customers with large DPF environments like are experiencing 
significant performance issues and 
apparent hangs due to contention when FCM resources are tuned 
automatically. The system 
controller thread (db2sysc) will adjust FCM resources downward 
after 30 minutes or more of low 
workload. During relatively quiet times, the resources can get 
adjusted down to very low values. 
This causes problems on systems with large workload bursts. When 
the workload increases dramatically, 
the FCM resources need to be adjusted upwards quickly and this 
is when performance issues due to latch 
contention in the dynamic adjustment code occurs. This problem 
gets worse on large DPF 
instances with many logical partitions configured.
Problem-Zusammenfassung:
**************************************************************** 
* USERS AFFECTED:                                              * 
* All DPF environments                                         * 
**************************************************************** 
* PROBLEM DESCRIPTION:                                         * 
* Customers with large DPF environments like are experiencing  * 
*                                                              * 
* significant performance issues and apparent hangs due to     * 
* contention when FCM resources are tuned automatically. The   * 
* system                                                       * 
* controller thread (db2sysc) will adjust FCM resources        * 
* downward                                                     * 
* after 30 minutes or more of low workload. During relatively  * 
* quiet                                                        * 
* times, the resources can get adjusted down to very low       * 
* values.                                                      * 
* This causes problems on systems with large workload bursts.  * 
* When                                                         * 
* the workload increases dramatically, the FCM resources need  * 
* to be                                                        * 
* adjusted upwards quickly and this is when performance issues * 
* due to latch                                                 * 
* contention in the dynamic adjustment code occurs. This       * 
* problem gets                                                 * 
* worse on large DPF instances with many logical partitions    * 
* configured.                                                  * 
**************************************************************** 
* RECOMMENDATION:                                              * 
* Customer should upgrade to v95 fixpack 6.                    * 
****************************************************************
Local-Fix:
Large DPF customers can set FCM resources to large fixed values. 
However, the downside is that this may cause node failures in 
cases when db2fcmr/db2fcms EDUs run out of FCM buffers/channels.
verfügbare FixPacks:
DB2 Version 9.5 Fix Pack 6a for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 7 for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 8 for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 9 for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 10 for Linux, UNIX, and Windows

Lösung
Document available in v95 fixpack 6 version. 
 
With this fix setting FCM_NUM_BUFFERS or FCM_NUM_CHANNELS to 
"<large number> automatic" will make sure that 
the system controller thread doesn't adjust resources down below 
the specified <large number> value.
Workaround
keiner bekannt / siehe Local-Fix
Bug-Verfolgung
Vorgänger  : APAR is sysrouted TO one or more of the following: IC68267 IC68270 
Nachfolger : 
Weitere Daten
Datum - Problem gemeldet    :
Datum - Problem geschlossen :
Datum - der letzten Änderung:
10.02.2010
01.11.2011
01.11.2011
Problem behoben ab folgender Versionen (IBM BugInfos)
9.5.FP6
Problem behoben lt. FixList in der Version